In the last few years, drip irrigation has become increasingly popular as a substitute for other irrigation methods, such as sprinkler and furrow irrigation, in the irrigation of crops. Generally, drip irrigation comprises supplying a small volume of water frequently to the root area of plants and trees, and confining the water supplied substantially to such root areas. As a consequence, the drip irrigation systems are essentially underground, thus reducing the loss of water through evaporation. This is most important in those areas where water supplies are deficient because substantially smaller quantities of water can be used for maintaining and sustaining crops than would be the case with conventional furrow or ditch irrigation. Moreover, because the ground surface is not flooded with water, as is the case with conventional sprinkler and furrow irrigation, cultivating equipment may be run along the paths between the crops being tended at any time rather than at those times between irrigation, when the irrigation ditches are free of water and mud.
Generally, such a drip irrigation system includes a main supply line connected to a supply of water under pressure, the main supply line being of such size as to carry all the water required for the system at a desired pressure and without undue fluid frictional losses. Usually with such systems, there will be connected to the main supply line, a plurality of feeder lines spaced along the main supply line at desired intervals, and depending upon the configuration of the plot of land being irrigated, for conveying water from the main supply line along crop or tree rows, the feeder tubes being flexible or rigid, and each being a relatively small diameter as compared to the main supply line, to carry a volume of water desired to be distributed therethrough without undue fluid frictional losses.
Spaced along each feeder tube are a plurality of water emitters, each being designed to distribute water from the feeder tube to a specific plant root area in a desired and uniform volume at frequent intervals. Conventional prior art emitters on the market have been comprised of a variety of forms, most being designed to supply water from about 0.5 to about 4 gallons of water per hour, per emitter. In its simplest form, emitters may be simply a flexible tubing of very small diameter or more intricate valving arrangements, including filters and the like. One of the difficulties with emitters produced in the past, and a common difficulty of drip irrigation systems, is the fact that the emitters become clogged, not only by soil compacted around the exit orifice of the emitters, which either clogs the orifice or jams the functioning of the valves for the emitter, but from sediment or minerals in the water supply itself. In any one particular system, the emitters are generally of the same construction, so that the emitters do not provide for or accommodate differences in pressure fluctuation in different areas of the particular drip irrigation system. Since some systems will be installed in land having a rolling typography, it will be understood that pressures will fluctuate in the main supply line as well as the feeder lines leading from the main supply line, thus causing variation in the quantity of water issuing from one emitter in the system as compared to another. Moreover, complicated valving arrangements in some emitters provide high initial cost which may be prohibitive, particularly in newly developing areas where it is most important to provide increased food production at as low a cost as possible.